1. Field of the Invention
The present invention relates to a shake correcting device, an image pickup apparatus, a shake correcting method, a program for performing, and a storage medium storing the program, and more particularly relates to a shake correcting device, an image pickup apparatus, a shake correcting method, a program for performing, and a storage medium storing the program, which are suitable for preventing such a phenomenon that white defects move around on a display screen of a camera or a video camera or the like having an electronic shake correcting unit mounted thereon.
2. Description of the Related Art
Conventional image stabilizing systems as employed in apparatuses such as video cameras include a type that detects shakes of the apparatus by an angular velocity sensor, uses an image pickup element, having more pixels than a standard image pickup element required by television broadcasting systems, and extracts preselected areas with the standard size of broadcasting systems from within the entire image pickup area of the image pickup element, according to shakes of the apparatus detected by the angular velocity sensor. A shake correcting device employing this type of image stabilizing system will be further described.
FIG. 8 is a schematic diagram showing an image of the image pickup area of an image pickup element. In the figure, reference numeral 601 designates the entire image pickup area of the image pickup element, and reference numerals 602 to 604 designate areas with the standard size of broadcasting systems. When performing no shake corrections, an area 603 positioned in the center of the entire image pickup area is extracted, selecting from the three areas, 602 to 604, and thus a video image is output. When performing a correction, a video image is output, extracted from an area selected from the entire image pickup area 601, but with a deviation, for example, to the area 602 or the area 604, in order to remove a shake of the apparatus, according to a signal from a unit for detecting shakes, not shown. With regard to the position of an area to be extracted, there is no limitation as long as the area extracted lies within the entire area 601, and the area can even be extracted from an arbitrary position within the entire area 601.
FIG. 9 is a block diagram showing, as an conventional example, the configuration of an image pickup apparatus portion of a video camera that has a shake correcting device of the area extraction system, described above, as a shake correcting unit, using an angular velocity sensor as a shake detection unit. An image pickup apparatus having a shake correcting device mounted thereon will be described below with reference to FIG. 9. In the figure, reference numeral 101 designates a lens unit, and reference numeral 102 designates a charge coupled device (CCD). A subject image is formed on the CCD 102 by the lens unit 101, and then photoelectrically converted by the CCD 102. The CCD 102 has more pixels than the standard CCDs required by broadcasting systems (for example, NTSC (National Television System Committee)). Reference numeral 104 designates a CCD drive circuit for driving the CCD 102. The CCD drive circuit 104 is designed to be able to select lines with respect to the direction V (the number of lines) in FIG. 8, described above, from the lines in the entire image pickup area of the CCD 102 in order to extract an area for a final output, wherein the selection is made upon a control instruction from a microcomputer 919 for camera system control, described later.
The reference numeral 601 in FIG. 8, mentioned above, designates the entire image size, and the reference numerals 602 to 604 designate examples with the standard image size according to broadcasting systems. In FIG. 8, when the lines starting from ya+1, which is xcex94ya lines below the uppermost line, are effective for example, the xcex94ya lines are read at a high speed, and thereafter the lines from ya+1 line are read out in the same timing as the case of using a CCD with the standard size with respect to a vertical synchronizing signal. Then, the remaining xcex94yb lines are read out again at a high speed, thus practically extracting lines of the standard image size with respect to the direction V.
Upon a control instruction from the microcomputer 919, the CCD drive circuit 104 controls the accumulating time of the signal charge in the CCD 102, thereby implementing an electronic shutter. Specifically, a high speed shutter is implemented by setting the accumulating time of the signal charge in the CCD 102 short, and a slow shutter is implemented by setting the accumulating time, described above, long.
Reference numeral 103 designates an analog signal processing section that performs a predetermined process on signals obtained from the CCD 102 to generate analogue image pickup signals. Specific examples of the analog signal processing section 103 are a CDS (Co-related Double Sampling) circuit, and an AGC (Automatic Gain Control) circuit. Reference numeral 106 designates a line memory that can store a digital image pickup signal for one line at least by a memory control circuit 107. Further, pixels can be read out from a predetermined address in the line memory 106 by the memory control circuit 107. Reference numeral 105 designates a camera signal processing section that has a built-in A/D converter and performs processing of digital signals to generate final output video signals. A digital image pickup signal stored in the line memory 106 includes more pixels than the standard image size of the CCD 102, keeping the large number of pixels. The memory control circuit 107 is designed to be able to select a top pixel to be read from the line memory 106, and to read pixels for the standard image size, upon a control instruction from the microcomputer 919, described in the following.
The microcomputer 919 performs control of the entire camera system including control of the CCD drive circuit 104, exposure control, white-balance control, variable power lens control, auto focus control, image stabilizing control. However, in FIG. 9, only a portion of these functions associated with shake correction is shown for brevity. Shake detection is performed with respect to the two axes in the pitch (vertical) direction and the yaw (horizontal) direction. Since the same control is performed for the two axes, FIG. 9 shows the control only for one direction. Reference numeral 111 designates an angular velocity sensor for detecting shakes of the camera. Reference numeral 112 designates a HPF (High Pass Filter) for cutting the DC component of angular velocity signals output from the angular velocity sensor 111. Reference numeral 113 designates an amplifier for amplifying angular velocity signals detected by the angular velocity sensor 111.
Reference numeral 114 designates an A/D converter incorporated into the microcomputer 919, which converts angular velocity signals in the two directions, described above, into digital signals to become angular velocity data. Further, a HPF 115 and a phase compensation filter 116 perform predetermined processes on this angular velocity data. The angular velocity data passes through a variable HPF 117. Then, an integrator 118 generates shake correction data for the vertical and horizontal directions. Reference numeral 120 designates a correction system controller, which corrects shakes according to outputs of the angular velocity sensor 111. The microcomputer 919 transmits data for correcting shakes in the vertical direction to the CCD drive circuit 104, and data for correcting shakes in the horizontal direction to the memory control circuit 107, respectively. As mentioned before, the CCD drive circuit 104 and the memory control circuit 107 change the position for extracting lines of the standard image size from the CCD 102, according to the respective data for correcting shakes.
Through this series of operations, lines of the standard image size, as designated by the reference numerals 602 or 604 for example, can be extracted from the entire image size 601 of the CCD 102, as shown in FIG. 8 described above, with a deviation from the center, which makes it possible to correct shakes caused by hand shakes or the like.
However, as will be described below, there has been a problem with the conventional image pickup apparatus, described above. When picking up an image by a slow shutter with a longer exposure time of the image pickup element than a single field period, the slower the shutter speed, the more apparent white defects in the image pickup apparatus (CCD) become. FIGS. 10A and 10B are diagrams showing white defects that appears in subject image field formed by image signals from the image pickup apparatus during electronic image stabilizing control. In FIG. 10A, symbols A, B, and C designate the white defects generated by a slow shutter. In the case that the image stabilizing control is performed in this state, when the extraction position of the standard image size lines is shifted, for example, 401xe2x86x92402xe2x86x92403 with respect to the entire image size 405, the white defects move around actually on a display screen 410 of the image pickup apparatus, as shown in FIG. 10B, causing a phenomenon that the display becomes very unsightly.
It is an object of the present invention to provide a shake correcting device, an image pickup apparatus, and a shake correcting method that can prevent white defects of an image pickup unit from moving around on a display screen, thereby eliminating unsightliness of displays in correcting shakes of subject images, according to image signals that are output by the image pickup unit that converts the subject images into video signals, as well as a program for performing the method and a storage medium storing the program.
To attain the above object, in a first aspect of the present invention, there is provided a shake correcting device for correcting a shake of a subject image, by processing an image signal which is output by an image pickup unit that converts the subject image into the image signal, the shake correcting device comprising an image pickup unit, and a control device that determines a state of white defects which appears in the subject image field formed by the image signal that stops a function of correcting a shake of the subject image when the state of the white defects is determined to be at a higher level than a predetermined level.
With the arrangement of the shake correcting device according to the first aspect, in correcting shakes of a subject image according to an image signal output by the image pickup unit that converts the subject image into an image signal, if the state of white defects in the image pickup unit is at a higher level than a predetermined level, then a shake correction function is stopped, and thus the white defects are kept from moving around on the display screen of the image pickup unit, thereby eliminating unsightliness of displays.
To attain the above object, in a second aspect of the present invention, there is provided a shake correcting device for correcting a shake of a subject image, by processing an image signal which is output by an image pickup unit that converts the subject image into the image signal, the shake correcting device comprising an image pickup unit, and a control device that stops a function of correcting a shake of the subject image when an image pickup time by the image pickup unit exceeds a predetermined period of time.
With the arrangement of the shake correcting device according to the second aspect, in correcting shakes of a subject image according to an image signal output by the image pickup unit that converts the subject image into an image signal, if an image pickup time of the image pickup unit exceeds a predetermined time, then the shake correction function is stopped, and thus the white defects are kept from moving around on the display screen of the image pickup unit, thereby eliminating unsightliness of displays.
Preferably, in the second aspect, the image pickup time of the image pickup unit is an electric charge accumulation time over which a light quantity of the subject image that is received by the image pickup unit is accumulated as an electric charge.
Further, to attain the above object, in a third aspect of the present invention, there is provided a comprising an image pickup unit that converts a subject image into an image signal, a shake correcting device that corrects a shake of the subject image, by processing an image signal which is output by an image pickup unit, the image pickup apparatus comprising the image pickup unit, and a control device that determines a state of white defects which appears in the subject image field formed by the image signal that stops a function of correcting a shake of the subject image when the state of the white defects are determined by the determining device to be at a higher level than a predetermined level.
With the arrangement of the image pickup apparatus according to the third aspect, a similar effect to that of the above first aspect can be obtained.
Still further, to attain the above object, in a fourth aspect of the present invention, there is provided an image pickup apparatus comprising a shake correcting device for correcting a shake of a subject image, by processing an image signal which is output by an image pickup unit that converts the subject image into the image signal, the an image pickup apparatus comprising the image pickup unit, and a control device that stops a function of correcting a shake of the subject image when an image pickup time by the image pickup unit exceeds a predetermined period of time.
Preferably, in the fourth aspect, the image pickup time of the image pickup unit is an electric charge accumulation time over which a light quantity of the subject image that is received by the image pickup unit is accumulated as an electric charge.
With the arrangement of the image pickup apparatus according to the fourth aspect, a similar effect to that of the above first aspect can be obtained.
To attain the above object, in a fifth aspect of the present invention, there is provided a shake correcting method for correcting a shake of a subject image, by processing an image signal which is output by an image pickup unit that converts the subject image into the image signal, the shake correcting method comprising determining a state of white defects which appears in the subject image field formed by the image signal, and stopping a function of correcting a shake of the subject image when the state of the white defects is determined in the determining step to be at a higher level than a predetermined level.
With the shake correcting method according to the fifth aspect, a similar effect to that of the above first aspect can be obtained.
To attain the above object, in a sixth aspect of the present invention, there is provided a shake correction method for correcting a shake of a subject image, by processing an image signal which is output by an image pickup unit that converts the subject image into the image signal, the shake correction method comprising stopping a function of correcting a shake of the subject image when an image pickup time of the image pickup unit exceeds a predetermined period of time.
With the shake correcting method according to the sixth aspect, a similar effect to that of the above first aspect can be obtained.
To attain the above object, in a seventh aspect of the present invention, there is provided a program for implementing a shake correction method for correcting a shake of a subject image, by processing an image signal which is output by an image pickup unit that converts the subject image into the image signal, the program comprising a determining module for determining a state of white defects which appears in the subject image field formed by the image signal, and a control module for stopping a function of correcting a shake of the subject image when the state of the white defects is determined to be at a higher level than a predetermined level.
To attain the above object, in an eighth aspect of the present invention, there is provided a program for implementing a shake correction method for correcting a shake of a subject image, by processing an image signal which is output by an image pickup unit that converts the subject image into the image signal, the program comprising a control module for stopping a function of correcting a shake of the subject image when an image pickup time of the image pickup unit exceeds a predetermined period of time.
To attain the above object, in a ninth aspect of the present invention, there is provided a computer-readable storage medium storing a program for implementing a shake correction method for correcting a shake of a subject image, by processing an image signal which is output by an image pickup unit that converts the subject image into the image signal, wherein the program comprises a determining module for determining a state of white defects which appears in the subject image field formed by the image signal, and a control module for stopping a function of correcting a shake of the subject image when the state of the white defects is determined to be at a higher level than a predetermined level.
To attain the above object, in a tenth aspect of the present invention, there is provided a computer-readable storage medium storing a program for implementing a shake correction method for correcting a shake of a subject image, by processing an image signal which is output by an image pickup unit that converts the subject image into the image signal, wherein the program comprises a control module for stopping a function of correcting a shake of the subject image when an image pickup time of the image pickup unit exceeds a predetermined period of time.
The above and other objects of. the invention will become more apparent from the following drawings taken in conjunction with the accompanying drawings.